The present invention concerns a device for the qualitative or quantitative measurement of a magnetically labelled analyte, which device includes a coil arrangement, formed of at least one measuring coil and a reference coil arranged in connection with it, for measuring the analyte from a sample absorbed in a test base, and from the signal of which coil arrangement a change in inductance correlating to the content of the magnetically labelled analyte is arranged to be detected. In addition, the invention also relates to a corresponding method.
Numerous methods and apparatuses for measuring magnetic particles, for example, in analytic tests, are known from the prior art. For example, Finnish patent number 113297 discloses an idea concerning the use of a so-called astatic coil arrangement for measuring an analyte from a sample absorbed in a test base. In it, the coil arrangement is used to detect a change in inductance correlating to the content of a magnetically labelled analyte.
The application of traditional coil technology to such an arrangement, however, is associated with significant problems relating, for example, to the sensitivity of the apparatus. Some examples of these are capacitive parasitic current in the coil loops. Another problem can be mentioned the asymmetry of the coils, which is caused by, for example, the manual winding of the coils.
The magnetism of magnetic particles and thus the change in inductance they create in a coil system is very insignificant compared, for example, to the error signals caused by the environment or the test base itself. Thus the measurement results obtained using the apparatus leave much to be desired.
In addition, due to the test bases according to the prior art, the reactions of the analyte on the test base take place on a very small scale, due, for example, to expensiveness of the reagents. Therefore the positioning of the test base relative to the device, for example, creates a challenging problem while wrong positioning can distort the test results. In addition, the test base places special demands particularly on wrapped coil constructions.
The solutions disclosed in PCT publications WO-2005111614 and WO-2005111615 also make known the application of coil devices in analytic rapid tests. They are based on detecting a change of inductance from a change in resonance frequency. When measuring the change in resonance frequency, the resonance peak of the LC circuit changes to a different frequency when the inductance of a coil or the capacitance of a capacitor changes. However, the low inductance of the coil creates a problem. Parasitic phenomena of all kinds can easily connect to a coil with a low inductance, and thus they can also be distinguished from the signal measured in the frequency form.
PCT publication WO 03/076931 A1 discloses yet another manner of measurement known from the prior art. It too is based on detecting changes in frequency.
Various so-called SQUID-type methods are also known. However, their operating principle demands operation at very low temperatures, at even close to absolute zero. This makes the apparatus complicated, for example, in POCT (point of care testing) applications.